Investigation of Mn incorporation into NiOOH electrocatalyst loaded on BiVO4 photoanode for enhanced photoelectrochemical water splitting: Experimental and theoretical approach

Loading of OER cocatalyst is an effective strategy to overcome the inherent poor charge separation of BiVO4. Incorporation of Mn-doped NiOOH electrocatalyst on the electrochemically deposited BiVO4 photoanode surface boost the PEC water oxidation. Here, the Mn-NiOOH/BiVO4 (10%) photoanode exhibited ∼2.6 and ∼1.7-fold higher photocurrent density (2.41 mA cm-2), compared with BiVO4 and BiVO4/NiOOH, respectively. Noticeably, it delivered the transient decay time (τ) of 1.83 s, which is ∼3.5 and ∼2.3-fold higher than the BiVO4 and BiVO4/NiOOH, besides the BiVO4/Mn-NiOOH (10%) utilizes 42.4 % of the photogenerated holes, whereas in BiVO4, it is only 17.06 %, and BiVO4/NiOOH exhibits 25.98 % for the water oxidation process. The enhanced PEC activity of the BiVO4/Mn-NiOOH photoanode is due to reduced photoinduced charge carrier’s recombination rate, facile interfacial charge transfer, and rapid hole consumption. Moreover, the higher efficiency of Mn-NiOOH cocatalyst is understood by employing DFT studies and revealed that Mn-NiOOH (10%) has lower formation energy than higher concentrations and infers that it requires the lower overpotential (2.37 V) than NiOOH (3.06 V). Overall, under illumination, Mn-NiOOH consumes the photogenerated holes from BiVO4 for the cyclic catalytic process of NiOOH, thus enhances the PEC performance.